Now, going back to (), we follow [1]} and [2]}, quantifying the convergence rate of \(x\)  by showing the convergence of \(\mathbb {E}[\Vert \hat{x}(x_k) - x_k\Vert ^2]\) . For any \(\epsilon >0\) , we say that \(x_k \in \mathcal {X}\)  is an \(\epsilon \) -nearly stationary solution if \(\mathbb {E}[\Vert \hat{x}(x_k) - x_k\Vert ^2] \le \rho ^2 \epsilon \) . In (), we hide the \(\rho \)  factors under the \(\mathcal {O}\)  notation, so our solution is \(\sqrt{n}K^{-2/5}\) -stationary.
